Alkaline catalyzed cellulose-epichlorohydrin reactions wherein cellulose is pretreated with aqueous salt solutions



United States Patent 3,382,029 ALKALINE CATALYZED CELLULOSE EPI- CHLOROHYDRIN REACTIONS WHEREIN CELLULOSE IS PRETREATED WITH AQUEOUS SALT SOLUTIONS John B. McKelvey, Ralph J. Berni, and Ruth R. Benerito, New Orleans, La., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Filed July 2, 1963, Ser. No. 292,788 4 Claims. (Cl. 8-120) This application is a continuation-in-part of Ser. No. 188,910, filed Apr. 19, 1962, now abandoned.

A nonexclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to the treatment of textile materials, more particularly to the treatment of cotton or other cellulosic textiles so as to form small quantities of cellulose ethers therein for the purpose of enhancing the normally rather deficient property of resilience.

Resiliency has been discussed and defined by the following sources:

H. Mark, Textile Research Journal, 16, 361 (1946).

H. Hotfmann, Textile Research Journal, 18, 141 (1948).

R. Meredith, Mechanical Properties of Textile Fibers, Chapter XVIII (1956).

With the conclusion that a resilient fiber is one that when manipulated in a bunch or bundle, such as in a fabric (a) offers a moderate resistance to compression and (b) springs back vigorously on release even after compression for some time. The property is measured by a well known trade device called a Monsanto Crease Tester in degrees of angular recovery for samples conditioned for 24 hours at 65% relative humidity and 25 C. and the result is called a conditioned crease angle. It is the average in the warp and filling directions in all cases reported herein. The value may also be measured in a wet condition when the fabric may possess 50% or higher of moisture content instead of the normal 67% and this is called the wet crease recovery angle. Since apparel and most cotton goods are worn or used in the dry state the conditioned crease recovery angle is usually considered by the trade to be of highest importance. It is to the task of development of the former, i.e., conditioned crease recovery, that the inventors efiorts have been directed.

In testing the results of those who may be considered to be prior art, including US. Patent No. 2,985,501, it has been found that the improvement of the desired configurational memory at 65 relative humidity and room temperature has not occurred. Indeed, it was on many instances actually lowered; instead of elevated. Explanation of'this phenomenon was given before the A.C.S. Division of Cellulose Chemistry in Chicago, September 1961, and is published in Journal of Applied Polymer Science, 7 (1963). In brief, it may be stated that heterogeneous reactions between epichlorohydrin and alkali cellulose are exceedingly complex as to the exact chemical nature of the cellulose ether formed and are further complicated by side reactions such as hydrolysis of the re- CHzClCH-OI-Iz muonrapid CH2OIIGHOHCHBO H NaCl OH- slower CH2ClCI-ICH2 NaPOr cellulose Cell ONa cello- CHzCHzO HCHz-0 -cell and in Equation 2 the regeneration of a second epoxide ring is not considered chemically sound. Rather it is thought that Williamson synthesis occurs between a second molecule of soda cellulose and the intermediate (b) above.

If, however, the alkali is not controlled by a third substance (such as SiO PO -"N -Cl it is thought intermediate (b) in Equation 2, or a linear graft of it, is hydrolysed to a cellulose glyceryl ether or linear graft of it. Our final cellulose derivative contains no greater quantity of bound chlorine than does the: untreated control. superficially, it is no diiferent in appearance than the products of US. Patent No. 2,985,501 except that the ethers obtained by us with controlled alkali have a much improved configurational memory over untreated cotton when dry; that is, they show resiliency. It is customary to attribute the development of new properties in a chemical molecule to either (a) change in configuration of the molecules or (b) to chemical reaction to produce a new form of matter or a combination of both. This we believe to have been accomplished by the development of the property resiliency in the fabric.

Substantially any cellulosic material containing hydroxyl groups can be employed in the present processes. Illustrative examples of such materials include cellulose derived from cotton, flax, ramie, and the like vegetable materials, wood cellulose, regenerated cellulose such as viscose rayon and the like, partial esters of cellulose such as partially acetylated cellulose, beta-propiolactone-reacted cellulose, and the like, partial ethers of cellulose such as partially cyanoethylated, partially aminoethylated, and partially carboxymethylated cellulose. In general, We prefer as starting materials cellulosic textile fabrics (whether unmodified or chemically modified) wherein the original fibrous character of the material has been retained.

In reacting the cellulosic material with epichlorohydrin substantially any apparatus usually employed in the etherification of cellulose fabrics can be used. For bench scale work, a jacketed cylinder thermostatically controlled filled with epichlorohydrin may be used. The fabrics can be rolled with glass netting and immersed in the etherifying fluid at any desired temperature. In another type reaction vessel, a covered stainless steel box may be used with the fabric either pinned on a tenter frame or lying on the bottom in an unstretched condition. The epichlorohydrin bath may be used over and over with addition of fresh reagent and the epichlorohydrin adhering to the fabric may be reclaimed. The duration of the reaction was found by experiment to be from 15-30 minutes, if the temperature is maintained at 50-95 C.

As indicated previously, the concentrations of pretreating baths are critical. In the case of the commercially available dodecahydrate of trisodium phosphate it was found at 80 C. (a convenient working temperature for most of the experiments) that the desired property of resiliency was not imparted to the cloth until a concentration of 35% by weight solution was used. Hence the range 35% by weight and upwards is desirable and such solutions must be padded on the fabric at a high enough temperature to prevent crystallization (75 C. was satisfactory).

The soluble silicates present no problem in pretreating in that fabric padding may be performed at room temperature. However, the soluble silicates are sold commercially on the basis of the Na O/SiO ratio in a number of ratios with corresponding properties and uses. Thus, in sodium ortho silicate the ratio is 2, metasilicate 1, C brand (Philadelphia Quartz Company) 1/2, Starso 121.8, B.W. 111.6, K brand 1:2.9, N brand 1:3.22, etc. For our purposes any of the ratios from 2:1 to 1:1.6 which would include sodium orthosilicate metasilicate and sesqui-silicate have been found to be advantageous if used at the following concentrations of active ingredients in water.

Minimum Useful Greater concentrations than these minima may be used, of course, as an operator skilled in the art may desire, the only restrictions being limits of solubility and cost.

Sodium azide may be used in the range 20% to saturation to impart resiliency.

Common salt (NaCl) solutions without any added alkali at 85 C. may also be used as a fabric pretreatment for reaction with epichlorohydrin. It was found that even 5% NaCl pretreatment caused 2.6% weight gain on the fabric in 4 hours reaction time but a 15% concentration imparted useful properties to it. Similar results were obtained with neutral salts such as LiCl, NaBr, NaI, and CaCl Furthermore, it was shown that caustic soda solution (2-15% by weight) when saturated with common salt likewise imparted resiliency to the fabric after reaction with epichlorohydrin. The desired results could be obtained in a matter of minutes with 15% NaOH solution saturated with salt at 85 C. However, pretreatments with caustic soda (2-15% by weight) in the absence of added salt did not give the desired property of resiliency.

Sodium orthosilicate saturated with salt in the range of 1520% orthosilicate also produced excellent results surpassing those of orthosilicate alone under identical conditions.

Our new process also differs from prior art US. Patent No. 2,985,501 in that when the precursors of epichlorohydrin (1,3 dichloro-2-propanol, 1,2 dichloro-3-propanol) are used instead of epichlorohydrin in the methods of application described previously, no dry resiliency in the fabric was obtained. See Example 6.

Likewise, when epichlorohydrin is treated with NaOH, KOH, etc., alone as shown in Table II, Journal of Applied Polymer Science, 7 (1963) by our new process dry resiliency was not found, in fact the results were usually lower than that found in untreated cotton fabric or no higher than that produced upon a control with alkali alone.

EXAMPLE 1 An 80 x 80 cotton fabric sample (approximately 5 g.) was padded twice with 40% Na SiO -5H O to approximately 100% wet pick-up and thereafter reacted at 80 C. in a 100 ml. stoppered graduated cylinder containing epichlorohydrin (approximately 80 ml.). The fabric was completely immersed in the epichlorohydrin and was reacted for 30 minutes. The fabric was then removed and the reaction quenched with tap water for a period of about 10 minutes. The fabric sample after quenching was soaked in a mild acid bath for about 5 minutes and was finally washed free from acid with water. Subsequent to washing, the fabric was ironed dry and moisture equilibrated overnight. The weight gain was 8.7% and the dry and wet crease angles (warp-l-fill) were 256 and 313 respectively. (All crease angles mentioned are Monsanto (warp-Hill) degrees.)

EXAMPLE 2 The procedure according to Example 1 was used except for the replacement of metasilicate with 20% aqueous Na SiO (orthosilicate). The treated fabric had a weight gain of 10.5% and the dry and wet crease angles were 249 and 308 respectively.

EXAMPLE 3 The procedure according to Example 2 except for the use of a 15 solution in place of the 20% solution of orthosilicate. The treated fabric had a weight gain of 5.8% and a dry and wet crease angle of 235 and 302 respectively.

EXAMPLE 4 Procedure according to Example 3 except for the use of 25% orthosilicate. The treated fabric had a weight gain of 16.0% and a dry and wet crease angle of 245 and 288", respectively.

EXAMPLE 5 Fabric (80 x 80) of approximately 20 g. was rolled in glass fiber cloth after being padded twice in 20% orthosilicate to 100% wet pick-up and completely immersed in a large 4 liter cylinder containing epichlorohydrin. The etherification reaction was carried out at a temperature of 78-80 C. for a period of 30 minutes. The resultant fabric had a 9.1% weight gain and a dry and wet crease angle of 254 and 286, respectively.

EXAMPLE 6 (Used to show that 1,3 dichloropropanol will not give high dry crease angle under the conditions used in the process of the instant invention.)

Fabric (5 g.) was treated as in Example 2 substituting 1,3 dichloropropanol for the epichlorohydrin. The treated fabric had a weight gain of 5% and a dry crease angle of only 163 which is less than the control fabric.

EXAMPLE 7 The process according to Example 5 except that the bath temperature was lowered to 6769 C. The resultant fabric had a weight gain of 9% and a dry crease angle of 242 C.

EXAMPLE 8 The process according to Example 5 except that the time was reduced to 20 minutes and temperature was reduced to 77 C. The treated fabric had a 10.5%

weight gain and a dry crease angle of 243 and a wet crease angle of 271.

EXAMPLE 9 Samples of x 80 fabric were treated as in Example 1 except that the type of sodium silicate as shown in the following table was varied.

Samples treated as in Example 1 but with type of silicate and weight gain varied.

Active Ingre- Silicate dients Used Percent Product in Treat- Weight Dry Angle Wet Angle ment (weight Gains percent) EXAMPLE .11

The procedure according to Example 1 except for the replacement of metasilicate with sodium azide solution (NaN and change of reaction temperature and time to C. and 46 hours, respectively. The treated fabric had a weight gain of 4.2% and a dry and wet crease angle of 255 and 250, respectively.

EXAMPLE 12 The procedure according to Example 1 except for replacement of metasilicate with 15% sodium sulfite and change in reaction temperature 'and time to 25 C. and 22 hours, respectively. The treated fabric had a weight gain of 1.1% and a dry and wet crease angle of 253 and 239, respectively.

EXAMPLE 13 The procedure according to Example 1 except for replacement of metasiiicate with Na PO 1211 0 1.8 NaOH (commercial trisodium phosphate) and padding the fabric at 65-750 C. to prevent crystallization of the phosphate. In the range of 30-50% .Na PO the weight gains of the fabrics were 4.25.9% with crease angles of 220-258 dry and 2l6-257 wet.

EXAMPLE 14 The procedure according to Example 1 except for replacement of metasilicate with 20% Na 'CO -2% NaOH mixture. The weight gain of the treated fabric was 3% and the dry and wet crease angle 233 and 286, respectively. The salt, sodium carbonate, used in absence of sodium hydroxide did not produce the desired increase in dry crease angle.

EXAMPLE 15 The procedure according to Example 1 except for replacement of metasilicate with a mixture of an aqueous solution of 20% -NaCl and 3% NaOH. The weight gain of the treated fabric was 4.5% and the dry and Wet angle was 226 and 261, respectively. The use of the sodium chloride in like amounts without the sodium hydroxide did not give the desired increase in dry crease angles.

EXAMPLE 16 An 80 cotton fabric padded with saturated NaCl solution and reacted 2 hours at 85 with pure epichlorohydrin exhibited a dry crease recovery at 236. At the end of 3.5 hours the value was 246. The weight gains were 2.6% and 4.1%, respectively.

EXAMPLE 17 The cotton fabric swatches padded with aqueous NaOH solution in the range of 2- 15%, after the caustic solution was saturated with common salt, showed dry crease recovery of 210-260, respectively. When sodium hydroxide alone was used the values ranged from 192- 218", respectively (control 196).

EXAMPLE 18 An 80 cotton fabric swatch was padded with 15% aqueous Na 'SiO saturated with common salt and held at for 15 minutes. The purified cloth showed dry crease recovery of 260. When 20% Na SiO saturated with salt was used, the recovery was 277. With 10% orthosilicate (saturated with salt) the gains were insignificant.

EXAMPLE 19 An 80 cotton fabric padded with 35% CaCl solution and held at 85 in epichlorohydrin for 7.3 hours showed dry crease recovery of 246.

EXAMPLE 20 An 80 cotton fabric padded with 5 M LiCl (21% dry weight) and held at 85 for '2 hours in epichlorohydrin showed dry crease recovery of 241 at 6.7% weight gain.

We claim? 1. In the process for crosslinking cellulosic textile fibers by reaction with an aqueous solution of epichlorohydrin and a hydroxyl ion-supplying catalyst therefor to increase the resiliency of said fibers, the improvement which comprises wetting the cellulosic textile fibers, prior to their reaction with epichlorohydrin, with an aqueous solution of a water soluble salt selected from the group consisting of sodium azide, sodium sulfite, and calcium chloride, the concentration of salt in said aqueous solution being from at least 15% by weight to saturation.

2. The process improvement of claim 1 wherein the water soluble inorganic salt is sodium azide applied as an aqueous solution at a temperature of at least about 25 C.

3. The process improvement of claim 1 wherein the water soluble inorganic salt is sodium sulfite applied as a aqueous solution at a temperature of at least about 25 C.

4. The process improvement of claim 1 wherein the water soluble inorganic salt is calcium chloride applied as an aqueous solution at a temperature of at least about 85 C.

References Cited UNITED STATES PATENTS 3,173,750 3/1965 McDowell 8116 3,194,627 7/ 1965 Gagarine 8-116 FOREIGN PATENTS 465,105 4/1937 Great Britain. 696,282 8/ 1953 Great Britain.

OTHER REFERENCES Lawrie et al.: Journal of the Society of Dyers and Colourists, January 1940, pp. 6-17, 8-120.

McKelvey ct al. I: American Dyestuff Reporter, vol. 49, pp. 804-809 (1960), 8- 116.

McKelvey et al. II: Journal of Polymer Science, vol. 51, pp. 209-230 (1961), 8-116.

MoKelvey et al. III: Journal of Applied Polymer Science, vol. 7, pp. 1371-1389 (1963), note the September 1961 presentation 8-1 16.

NORMAN G. TORCHIN, Primary Examiner.

J. CANNON, Assistant Examiner. 

1. IN THE PROCESS FOR CROSSLINKING CELLULOSIC TEXTILE FIBERS BY REACTION WITH AN AQUEOUS SOLUTION OF EPICHLOROHYDRIN AND A HYDROXYL ION-SUPPLYING CATALYST THEREFOR TO INCREASE THE RESILIENCY OF SAID FIBERS, THE IMPROVEMENT WHICH COMPRISES WETTING THE CELLULOSIC TEXTILE FIBERS, PRIOR TO THEIR REACTION WITH EPICHLOROHYDRIN, WITH AN AQUEOUS SOLUTION OF A WATER SOLUBLE SALT SELECTED FROM THE GROUP CONSISTING OF SODIUM AZIDE, SODIUM SULFITE, AND CALCKUM CHLORIDE, THE CONCENTRATION OF SALT IN SAID AQUEOUS SOLUTION BEING FROM AT LEAST 15% BY WEIGHT TO SATURATION. 